This invention relates to a method for co-hydrolyzing silanes of the formulas HSi(OR).sub.3 and Si(OR).sub.4 to form soluble resinous co-hydrolysates. The invention also relates to the soluble co-hydrolysates formed thereby as well as the method of using said co-hydrolysates to provide coatings on various substrates, including electronic devices.
It is known in the prior art that organotrialkoxysilanes dissolved in a solvent are readily hydrolyzed by water in an acidic environment. See, for example, Eaborn, "Organosilicon Compounds", Butterworth's Scientific Publications, London (1960) p 301. The resultant hydrolysates, however, can be unstable and often condense upon formation to yield insoluble organopolysiloxane gels.
Similar hydrolysis and condensation reactions are also known to occur in hydridosilanes (silanes with an Si--H bond) with organoxy functional groups. The Si--H bonds of these silanes, however, are susceptible to cleavage resulting in the production of insoluble gels. For instance, Muller in Chem Tech 2, 7-13, 41-49 (1950) teaches that the hydrolysis of triethoxysilane to silanetriol in an alcohol results in the production of an insoluble gel.
Levene in U.S. Pat. No. 3,811,918 teaches the formation of a gel resistant glass precursor composition which may be heated to form a protective glass coating. The coating composition is formed by a partially hydrolyzing a silicon alkoxide in a solvent, reacting the partial hydrolysate with an aqueous solution of a metal oxide forming compound, hydrolyzing this solution with additional water and then adding an acid to form a stable, gel-free solution. The reference, however, does not disclose co-hydrolyzing silanes.
Hayes in U.S. Pat. No. 4,395,563 teaches a method of hydrolyzing an alkoxysilane in which the alkoxysilane is mixed with a stoichiometric excess of water and an acid catalyst. The resultant hydrolysis mixture is then neutralized and the hydrolysis products separated. Again, however, this reference fails to teach co-hydrolysis of silanes.
It has now been unexpectedly found that the process of the present invention provides a method for co-hydrolyzing silanes to form soluble resins which may be used to form coatings.